Junk E-mail Levels Drop After Big Spammer Goes Silent

The number of spam e-mail messages circulating on the Internet tumbled at the end of December after the world’s largest spamming operation mysteriously went dark on Christmas Eve. A network of malware-infected computers known as the Rustock botnet, which is widely believed to be Russian-operated and had been responsible for about half of all spam globally, “appears to have completely gone off the map and is yet to resume,” said Matt Sergeant, senior anti-spam technologist at MessageLabs, a unit of the security-software maker Symantec.